Input devices including proximity sensor devices (also commonly referred to as touchpads or touch sensor devices) are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region, often demarked by a surface, in which the proximity sensor device determines the presence, location, and/or motion of one or more input objects. Proximity sensor devices may be used to provide interfaces for the electronic system. For example, proximity sensor devices are often used as input devices for larger computing systems (such as opaque touchpads integrated in, or peripheral to, notebook or desktop computers). Proximity sensor devices are also often used in smaller computing systems (such as touch screens integrated in cellular phones).
Proximity sensors may operate by detecting changes in an electric field and/or capacitance in the sensing region. In order to detect such changes, the proximity sensors may first determine a “baseline” (e.g., indicating a state of the electric field when no input object is expected to be present) for one or more portions of the sensing region. However, establishing an incorrect baseline may cause the proximity sensors to report “ghost” touches (e.g., false positives) and/or fail to report intentional touches (e.g., false negatives). Many factors may contribute to an incorrect baseline estimate including, for example, moisture and/or other objects in contact with the sensing region when attempting to detect a user input. Thus, it is desirable to filter ghost touches from intentional touches when processing user inputs from the sensing region.